Root-knot nematodes (RKNs; Meloidogyne spp.) are a major constraint of pepper (Capsicum annuum L.) crops worldwide. In Mexico, Sinaloa State is one of the main producers of pepper; however, there is little information available on the distribution, prevalence, and incidence of RKN on this crop. Identification of RKN species and estimation of the epidemiological factors are important to design its management strategies. A total of 190 RKN samples from Los Mochis, Culiacan, La Cruz, and Escuinapa areas of Sinaloa were collected from pepper plants at production stage under greenhouse conditions, to analyze the distribution, prevalence, and incidence of RKN. Primary identification of RKN species was based on perineal pattern morphology and confirmed by molecular SCAR marker–based identification. RKNs were found in all the surveyed greenhouses of pepper, confirming their absolute distribution and prevalence in this crop. Meloidogyne enterolobii, Meloidogyne incognita, and Meloidogyne javanica were identified in the four areas. Overall incidence of M. enterolobii, M. incognita, M. javanica, and mix of M. enterolobii + M. incognita was 63.7, 11.7, 12.8, and 11.7%, respectively, indicating that RKNs are a serious threat for pepper and other crops in Sinaloa State. This information will enable pepper growers to design and implement an appropriate control for RKN species.

Antecedentes: Las rizobacterias promotoras del crecimiento vegetal (PGPR) y hongos micorrízicos arbusculares (AMF) son alternativos para el manejo sustentable del cultivo de chile. Objetivo: Investigar los efectos benéficos de la inoculación de PGPR y AMF en el crecimiento de plantas de pimiento morrón. Métodos: Se utilizaron dos cepas de PGPR (Pseudomonas tolaasii P61 y Bacillus pumilus R44), su mezcla, y un control no inoculado, y su combinación con un consorcio de AMF (Funneliformis aff. geosporum y Claroideoglomus sp.). Se realizó un experimento factorial 4x2 [cuatro niveles para bacterias (Control, P61, R44, y la mezcla de ellas) y dos niveles de AMF (no-AMF y AMF)], en invernadero por 80 días después de la inoculación. Los AMF se inocularon al momento de la siembra, y las PGPR 15 días después de la emergencia de las plántulas. Resultados y conclusiones: El control no inoculado mostró menor crecimiento comparado con plantas con PGPR y AMF, solos o combinados. Las plantas con P61 y en combinación con R44+AMF tuvieron mayor crecimiento. Los AMF mejoraron la eficiencia fotoquímica de PSII en comparación con plantas control, plantas inoculadas con R44, o la mezcla bacteriana. Tanto PGPR como AMF mejoraron el crecimiento y el vigor de las plantas.

Plant growth promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF) are a biological alternative for the sustainable management of Capsicum annuum L. This research work evaluated the effects of both PGPR and AMF on bell pepper and jalapeno pepper plants. Five bacterial strains isolated from several locations in Estado de Mexico were used: [P61 (Pseudomonas tolaasii), A46 (P tolaasii), R44 (Bacillus pumilus), BSP1.1 (Paenibacillus sp.), and OLs-Sf5 (Pseudomonas sp.)], and three treatments with AMF [H1 (consortium isolated from pepper crops in the State of Puebla), H2 (Rhizophagus intraradices), and H3 (consortium isolated from the rhizosphere of lemon trees, State of Tabasco)]. In addition, a fertilized treatment (Steiner nutrient solution at 25%) and an unfertilized control were included. Seedlings of "Caloro" jalapeno pepper and "California Wonder" bell pepper were inoculated with AMF at seed sowing, and PGPR were inoculated after 15 days of seedling emergence; seedlings were grown under plant growth chamber conditions. P61 bacterium and H1 AMF consortia were the most effective microorganisms for jalapeno pepper whereas R44 bacterium and AMF H3 and H1 were the most effective for bell peppers, when compared to the unfertilized control. Furthermore, P61 and R44 bacteria showed beneficial effects on PSII efficiency. (C) 2017 Asociacion Argentina de Microbiologia. Published by Elsevier Espana, S.L.U.

The use of Lagenaria siceraria rootstocks in watermelon production has favored fruit yield and quality under conditions of environmental stress. However, it is necessary to know if the differential characteristics of fruit and seed L. siceraria are related to watermelon yield and fruit in grafted plant. The objective was to evaluate two dissimilar groups of Mexican L. siceraria as rootstock in Tri-X 33 watermelon variety to relationship the morphological characteristics of rootstock with productive variables and fruit quality. The treatments were Tri-X 313 variety ungrafted and grafted with accessions of group 1 (L46 and L56) and group 2 (L48, L50 and L54). Variables evaluated were fruit and yield and quality parameters. No differences were found between groups of L. siceraria in fruit yield and external quality parameters. With the exception of pulp firmness and luminosity, LG1 surpassed group LG2 by 30.7 and 5.0%, respectively. While, when comparing grafted and ungrafted plants, it was found that grafted plants were superior, with increases of 277.8% in number of fruits per m², 330.2% in commercial production, 54.6% in rind thickness, 85.2% in external firmness and 36.3% in chroma value of fruit pulp. Meanwhile, pulp percentage and hue were reduced by 13.8% and 15.5%, respectively, in grafted watermelons. Thus, the seed and fruit characteristics are not sufficient criteria to select L. siceraria rootstocks for watermelon production.

Lettuce is the most consumed leafy crop worldwide and the high levels of nitrates in its leaves can be carcinogenic. The objective of this study was to evaluate the effect of different nitrate/ammonium ratios in the nutrient solution and two light intensities (200 and 400 μmol·m⁻²·s⁻¹) on the growth and nutrient concentration of lettuce plants under hydroponic conditions. Controlled environment chambers (light and temperature) and a floating root system were used with the application of Steiner's nutrient solution modified for each of the treatments. Treatments consisted of combinations of three nitrate/ammonium ratios (100/0, 75/25, and 50/50) and two LED light intensities. The variables evaluated were root volume, fresh and dry weight of the leaves, dry weight of the root, total dry weight and the mineral composition of the leaves. The experimental design was completely randomized with a 3 × 2 factorial arrangement with six repetitions. For the statistical analysis of the data, an analysis of variance and a comparison of means test were performed (Tukey, p≤0.05). The results showed that increasing the proportion of ammonium reduced the volume and dry weight of the root without affecting the fresh weight of the leaf. Increasing the light intensity increased the root volume and the fresh and dry weight of the leaves, while ammonium reduced the levels of potassium, calcium and nitrates in the leaves, especially when an intensity of 400 μmol·m⁻²·s⁻¹ was applied. These results suggest that optimizing nitrate/ammonium ratios and light conditions improves biomass production and nutritional quality of hydroponic lettuce.

Se evaluó el impacto de diferentes niveles de integral de luz diaria (DLI), desde 8,6 a 22,68 mol·m⁻²·d⁻¹, sobre la calidad de plántulas de chile pimiento (Capsicum annuum L.), haciendo uso de la iluminación LED blanca. Las variables en estudio fueron el índice de área foliar, relación raíz-vástago, compacidad e índice de calidad. Se utilizó un diseño experimental aleatorizado 2x4, evaluando dos niveles de PPFD (200 y 350 µmol·m-2·s−1) y cuatro fotoperiodos (12, 14, 16 y 18 h·d−1). Se aplicaron ocho tratamientos (DLI) con cuatro repeticiones cada uno. La interacción entre una PPFD de 200 µmol m-2·s−1 y un fotoperiodo de 14 h·d−1 produjo un mayor índice de área foliar; mientras que, la relación raíz-vástago, compacidad e índice de calidad de plántula, fueron características que destacaron cuando la PPFD de 350 µmol·m-2·s−1 se combinó con el fotoperiodo de 12 h·d−1. Estos resultados son fundamentales para la agricultura en ambientes controlados, porque permiten estandarizar protocolos de iluminación que aseguren plántulas de alto vigor para el trasplante, promoviendo al mismo tiempo el uso eficiente de la energía y reduciendo los costos operativos en la producción de hortalizas.